The invention relates to a modular circuit construction having more than one logic element for different logic functions to which input signals to be combined are applied in the form of input pulses of longer or shorter duration, and by which, an output pulse is supplied as output signal.
Data processing systems comprise a large number of units that must receive signals from superordinate or subordinate other units or must supply signals thereto. In systems having an intermediate-level or central control unit such signals must be exchanged with comparatively short transmission times. Such systems also call for maximum centralization of functions with attendant economy of hardware.
The use of integrated circuits in the form of modular circuits capable of performing a maximum number of functions is of particular advantage to the interfaces of the individual units of such data processing systems. Moreover, optimum economy can be achieved if only a few types of such modular circuits are employed.
This accounts for the demand for versatile modular circuits. Therefore, it is of advantage to employ a modular circuit that carries out internal changes or switching responsive to control signals with a view to changing the functions it is capable of performing.
Instances of programmable logic circuits having variable functions in which different operations can be defined have been reported in the literature through the action of external electric signals (cf. "Siemens-Schaltbeispiele" 1974/75, pp. 139-141 "Universeller Zeit- und Zahlerbaustein").
West German Auslegeschrift No. 1,943,844 corresponding to U.S. Pat. No. 3,500,158 describes an integrated semiconductor circuit for the mutual allocation of input and output signals as a function of a given binary code in which a plurality of circuit stages are provided with logic elements and control elements. The control elements in such circuits have a first and a second state of transmission in which a control circuit is provided with input connections to the logic elements for the selective control thereof in accordance with a given binary code. An operating input circuit is provided in this circuit arrangement having current paths connected to the control elements and causing the permanent switching of the control elements from the first to the second state of transmission as a function of control signals applied thereto and in accordance with the given binary code.
An object of the invention is to provide an integrated modular circuit having great versatility and, hence, capable of performing a comparatively large number of different functions.
It is another object of the invention to provide a modular logic circuit capable of performing on the interface of various units in a data processing system or the like the tasks of signal receivers or signal transmitters or carry out logic operations and thereby evaluate condition signals in such units.